1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera of the type that in-focus position adjustment of a photographing optical system is performed during assembly.
2. Related Art Statement
In a conventional camera having a zoom lens, it has been usual to perform, when assembled, in-focus position adjustment (hereinafter referred to as fc adjustment) of a photographing optical system and adjustment (hereinafter referred to as Zp adjustment) for making a difference in amount of the fc adjustment between a wide-angle state and a telephoto state of the zoom lens not larger than a predetermined value.
Taking a zoom lens barrel disclosed in U.S. Pat. No. 4,945,372, assigned to the applicant, as an example, a description will be given of how the fc adjustment and the Zp adjustment have conventionally been carried out. The teachings of U.S. Pat. No. 4,945,372 are incorporated herein by reference thereto.
FIG. 8 is a sectional view showing the disclosed zoom lens barrel.
The zoom lens barrel has a cam ring 124 fitted radially outwardly of a stationary frame 122 in a rotatable manner which is fixed to a camera body (not shown). A movable frame 128 is fitted radially inwardly of the stationary frame 122, with a second group frame 136 and a third group frame 150 being fitted radially inwardly of the movable frame 128. Further, an adjuster ring 126 is screwed to a distal end of the cam ring 122 and a retainer ring 127 is fixed in a circumferential groove at a distal dnd of the stationary frame 122. A stepped portion formed by the retainer ring 127 and the stationary frame 122 serves to restrict a movement the adjuster ring 126 in the direction of an optical axis. Radially outwardly of the cam ring 124, an interlock plate 156 is fixed by screws to be integral therewith. A geared portion 157 is provided around an outer circumference of the interlock plate 156, and an arm 165b of a frame 165 and an arm 166b of a frame 166, both being provided in a finder lens group, are arranged to respectively come into abutment against opposite end faces 155a, 155b of the interlock plate 156 in the direction of the optical axis. Note frames 65 and 66 of finder 16 in FIG. 3 of U.S. Pat. No. 4,945,372.
A first lens group 131 is held by the movable frame 128 through a first group frame 134, a second lens group 132 is held by the second group frame 136 through a front group holding frame 142 and a rear group holding frame 144, and further a third lens group 133 is held by the third group frame 150 through a holder frame 154, respectively.
Operation of the above prior art thus constructed will be explained below.
When the geared portion 157 receives an output from a zoom drive unit (not shown), the cam ring 124 fixed to be integral with the interlock plate 156 is rotated about the optical axis with respect to the stationary frame 122. The rotation of the cam ring 124 causes the first lens group 131, the second lens group 132 and the third lens group 133 to move through respective appropriate distances in the direction of the optical axis according to the relationship between a straightforward groove defined in the stationary frame 122 and a cam groove defined in the cam ring 124.
The Zp adjustment is provided to make a difference in amount of the fc adjustment between a wide-angle state and a telephoto state of the zoom lens not larger than a predetermined value, as mentioned above, and is carried out, for example, in the foregoing prior art by moving the holder frame 154 back and forth with respect to the third group frame 150.
The fc adjustment is carried out in the foregoing prior art by rotating the adjuster ring 126 to move the cam ring 124 back and forth in the direction of the optical axis with respect to the stationary frame 122, thereby moving the first lens group 131, the second lens group 132 and the fourth lens group 133 back and forth in the direction of the optical axis.
With the fc adjustment carried out in the prior art as explained above, however, the position of the cam ring 124 in the direction of the optical axis is not definite with respect to the stationary frame 122, i.e., the camera body (not shown).
On the other hand, a finder unit (not shown) is fixed to the camera body. Therefore, if the arm 165b of the frame 165 and the arm 166b of the frame 166 are not in preset reference positions with respect to the camera body, the lens-to-lens spacing in the finder would not be determined by the fixed positions and hence the relationship between the photographing lens and the finder could not be kept normal. Accordingly, adjusting means has been required which is used to shift the position of the interlock plate 156 with respect to the cam ring 124 in the direction of the optical axis after carrying out the fc adjustment, so that the interlock plate 156 is always located at a fixed position with respect to the camera body and the finder.
Further, because of the need of adjusting the relative position between the cam ring 124 and the interlock plate 156 fixed to each other, as mentioned above, the cam ring 124 and the interlock plate 156 can not be formed into a one-piece unit, thus resulting in a larger number of parts and an increased cost.